Biocidal polyurethane and its antibacterial properties

The antimicrobial finishes on the cotton fabrics has been known and reported recently. Particularly, the reactive-antimicrobial finishes are the most attractive. In this study, we synthesized three types of polyurethane (PU) polymers; type A (molecular weight of polytetramethylene glycol (PTMG) is 2000), type B (molecular weight of PTMG is 1000), and type C (molecular weight of PTMG is 650). Firstly, the PU prepolymers were prepared by reacting PTMG with 4,4′-diphenylmethane diisocyanate (MDI), then were extended with diethylenetriamine (DETA) (or DETA/hydrazine mixture) to form the PU polymer. The polymer was then grafted with epichlorohydrin and further reacted with different amounts of biocide (QAS) to form biocidal active PU quaternary ammonium salts. The biocidal properties of the PU films were evaluated by the agar plate and the shake flask method. From the experimental results, it demonstrates that these films and finished fabrics exhibit a high biocidal activity against Staphylococcus aureus. The biocidal activity is found to increase with the amount of QAS. After rinsing with water, the biocidal characteristics of these films and finished fabrics remain. From IR spectra, PU films with covalent bond of QAS show an absorption peak at 2300 cm⁻¹, which corresponds to the presence of silicon in QAS. For the mechanical properties, the PU films with QAS sustain the mechanical properties in spite of the increasing amount of grafted QAS.